The Applicant's Document EP-A-0 667 271 describes a swivel coupling for coupling together two rail vehicles. That swivel coupling rests on a shared bogie between said two rail vehicles, and it comprises:
a toroidal part connected to one of the vehicles; PA1 a support part connected to the other vehicle; PA1 a cylindrical pivot fixed to a soleplate, and engaged in a cylindrical bore; and PA1 a toroidal swivel element fixed to said soleplate and enabling said soleplate to swivel relative to said toroidal part. PA1 the swivel coupling comprises: PA1 a toroidal central part having a frustoconical bearing surface; PA1 a ball having a hollow conical central portion that fits over the frustoconical bearing surface of the toroidal central part; PA1 resilient elements; PA1 a disk; and PA1 a holding screw including a vertical pivot; PA1 the top portion of the toroidal part is provided with the frustoconical bearing surface, and its bottom portion is connected to the underframe of the body of one of the vehicles; PA1 the ball associates a first element that is spherical in overall shape with a second element that is external and that is disposed to rotate freely on the first element; PA1 there are two resilient elements, and they are semi-circular in overall shape and are disposed symmetrically on either side of the ball and of the longitudinal axis of the vehicle so as to bear against the outside surface of the second element of the ball; PA1 the disk is disposed between the underframe of the body of one of the vehicles and a support part for supporting the swivel coupling; PA1 the disk holds the second element of the ball on the first element of the ball; PA1 the support part is connected to the underframe of the body of one of the vehicles; PA1 the support part supports the toroidal central part via the bottom portion thereof; PA1 the vertical pivot of the holding screw is engaged in the center of the toroidal central part, and it is fixed thereto by means of thread; and PA1 the bottom portion of the toroidal central part is recessed to receive the body/bogie drive.
A toroidal swivel element enables a soleplate to swivel relative to the toroidal part.
That toroidal swivel element is a structure made up of multiple successive layers of metal and of rubber that can be of stiffnesses that are different and that vary progressively.
A major drawback with the swivel coupling for coupling together two rail vehicles as described in the prior art document is that the angular displacements which it permits are small.
In the particular case of body-tilting vehicles, the swivel coupling for coupling together two rail vehicles as described in the prior art document cannot accommodate displacement about the longitudinal axis without producing an opposing force.
The fundamental drawback of such an opposing force is that it twists the body.
The swivel coupling for coupling together two vehicles as described in the prior art document suffers from the drawback of being stiff and therefore of twisting the bodies of body-tilting vehicles as they go round curved portions of track.